Olefin-based polymer and preparation method thereof

ABSTRACT

The present invention relates to an olefin-based polymer which exhibits superior processability and superior adhesive properties and therefore is desirably applicable to a hot-melt adhesive (HMA) or the like, and a preparation method thereof. The olefin-based polymer has a molecular weight distribution (Mw/Mn, PDI) of 2˜3, and a density of 0.85 to 0.88 g/cm 3 , and satisfies the relation of Tc−Tm&gt;0, wherein Tc (° C.) is a crystallization temperature and Tm (° C.) is a melting point.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/703,236, filed Dec. 10, 2012, which is a National Stage Entry ofInternational Application No. PCT/KR2011/004859, filed Jul. 1, 2011, andclaims the benefit of Korean Application No. 10-2010-0063578, filed onJul. 1, 2010, which are hereby incorporated by reference in theirentirety for all purposes as if fully set forth herein.

TECHNICAL FIELD

The present invention relates to an olefin-based polymer and apreparation method thereof. More particularly, the present inventionrelates to an olefin-based polymer which exhibits superiorprocessability and superior adhesive properties and therefore isdesirably applicable to a hot-melt adhesive (HMA) or the like, and apreparation method thereof.

BACKGROUND ART

Preparation and application of polyolefins have been rapidly developedwith a development of a catalyst called a Ziegler-Natta catalyst, and avariety of production processes and applications of the products havebeen also developed. Recently, metallocene catalysts have been commonlyused in the preparation of polyolefins, and metallocene catalystsdiscovered by kaminsky's group in 1980 are composed of a transitionmetal as a main catalyst and an organic aluminium compound as aco-catalyst. The metallocene catalyst is a homogeneous complex catalysthaving a single active site, and produces polymers with a narrowmolecular weight distribution and a uniform comonomer distributionaccording to the single-site characteristics. In addition, themetallocene catalyst has the properties of controlling thestereoregularity, copolymerization characteristics, molecular weight,crystallinity, and so forth of the obtained polymer by changing theligand structure of the catalyst and the polymerization conditions.

Meanwhile, there have been attempts to apply an olefin-based polymerprepared by using the metallocene catalyst to hot-melt adhesive (HMA),and the hot-melt adhesive is required to exhibit superior meltprocessability and superior adhesive properties at low temperature.However, since most of the previously known olefin-based polymers didnot satisfy both of the melt processability and the adhesive properties,there has been a limit in their application to the hot-melt adhesive.

SUMMARY OF THE INVENTION

The present invention relates to an olefin-based polymer which exhibitssuperior processability and superior adhesive properties and thereforeis desirably applicable to a hot-melt adhesive (HMA) or the like, and apreparation method thereof.

Accordingly, the present invention provides an olefin-based polymer thathas a molecular weight distribution (Mw/Mn, PDI) of 2˜3, and a densityof 0.85 to 0.88 g/cm³, and satisfies the relation of Tc−Tm>0, wherein Tc(° C.) is a crystallization temperature and Tm (° C.) is a meltingpoint.

Further, the present invention provides a preparation method of theolefin-based polymer, including the step of polymerizing olefin-basedmonomers in the presence of a catalyst composition including atransition metal compound of the following Chemical Formula 1 and one ormore co-catalysts selected from the group consisting of the followingChemical Formulae 4 to 6:

wherein R1 and R2 are the same as or different from each other, and eachindependently hydrogen; an alkyl radical having 1 to 20 carbon atoms; analkenyl radical having 2 to 20 carbon atoms; an aryl radical having 6 to20 carbon atoms; a silyl radical; an alkylaryl radical having 7 to 20carbon atoms; an arylalkyl radical having 7 to 20 carbon atoms; or aGroup 4 metalloid radical substituted with hydrocarbyl; or R1 and R2 ortwo R2s may be connected to each other by an alkylidene radicalcontaining an alkyl radical having 1 to 20 carbon atoms or an arylradical having 6 to 20 carbon atoms so as to form a ring;

R3s are the same as or different from each other, and each independentlyhydrogen; a halogen radical; an alkyl radical having 1 to 20 carbonatoms; an alkenyl radical having 2 to 20 carbon atoms; an aryl radicalhaving 6 to 20 carbon atoms; an alkylaryl radical having 7 to 20 carbonatoms; an arylalkyl radical having 7 to 20 carbon atoms; an alkoxyradical having 1 to 20 carbon atoms; an aryloxy radical having 6 to 20carbon atoms; or amido radical; or two or more of R3s may be connectedto each other so as to form an aliphatic or aromatic ring;

CY1 is a substituted or unsubstituted aliphatic or aromatic ring, inwhich CY1 may be substituted with a halogen radical; an alkyl radicalhaving 1 to 20 carbon atoms; an alkenyl radical having 2 to 20 carbonatoms; an aryl radical having 6 to 20 carbon atoms; an alkylaryl radicalhaving 7 to 20 carbon atoms; an arylalkyl radical having 7 to 20 carbonatoms; an alkoxy radical having 1 to 20 carbon atoms; an aryloxy radicalhaving 6 to 20 carbon atoms; or an amido radical; or if a plurality ofsubstituents are present, two or more thereof may be connected to eachother so as to form an aliphatic or aromatic ring;

M is a Group 4 transition metal; and

Q1 and Q2 are the same as or different from each other, and eachindependently a halogen radical; an alkyl radical having 1 to 20 carbonatoms; an alkenyl radical having 2 to 20 carbon atoms; an aryl radicalhaving 6 to 20 carbon atoms; an alkylaryl having 7 to 20 carbon atoms;arylalkyl radical having 7 to 20 carbon atoms; an alkyl amido radicalhaving 1 to 20 carbon atoms; an aryl amido radical having 6 to 20 carbonatoms; or alkylidene radical having 1 to 20 carbon atoms,

—[Al(R8)-O]_(n)—  [Chemical Formula 4]

wherein R8s are the same as or different from each other, and eachindependently halogen; a hydrocarbon having 1 to 20 carbon atoms; or ahydrocarbon having 1 to 20 carbon atoms which is substituted withhalogen; and n is an integer of 2 or more;

D(R8)₃  [Chemical Formula 5]

wherein R8 is the same as defined in Chemical Formula 4; and D is analuminium or boron;

[L-H]⁺[ZA₄]⁻ or [L]⁺[ZA₄]⁻  [Chemical Formula 6]

wherein L is a neutral or cationic Lewis acid; H is a hydrogen atom; Zis an element of Group 13; and As are the same as or different from eachother, and each independently an aryl group having 6 to 20 carbon atoms,or an alkyl group having 1 to 20 carbon atoms, at which one or morehydrogen atoms are unsubstituted or substituted with halogen,hydrocarbon having 1 to 20 carbon atoms, alkoxy, or phenoxy.

ADVANTAGEOUS EFFECTS

It was revealed that the olefin-based polymer according to the presentinvention has a narrow molecular weight distribution, a low meltingpoint, and a relatively high crystallization temperature so as toexhibit superior processability and superior adhesive properties at thesame time. The olefin-based polymer can be prepared by polymerization ofolefin-based monomers using a particular transition metal compound andco-catalyst.

Therefore, it was found that the olefin-based polymer can be verydesirably applied to hot-melt adhesives (HMA) or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a relationship between viscosity and shearrate of the olefin-based polymers of Examples 1, 4 and 5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an olefin-based polymer according to specific embodimentsof the present invention and a preparation method thereof will bedescribed.

According to one embodiment of the present invention, provided is anolefin-based polymer that has a molecular weight distribution (Mw/Mn,PDI) of 2˜3, and preferably 2˜2.5, and a density of 0.85 to 0.88 g/cm³,and preferably 0.855 to 0.875 g/cm³, and satisfies the relation ofTc−Tm>0, preferably more than 0 and 30 or less, and more preferably 5 ormore and 20 or less, wherein Tc (° C.) is a crystallization temperatureand Tm (° C.) is a melting point.

As substantiated by the following Examples, the experimental results ofthe present inventors showed that an olefin-based polymer having arelatively narrow molecular weight distribution and a low density, andsatisfying the relation of Tc−Tm>0, wherein Tc is a crystallizationtemperature and Tm is a melting point, can be provided by polymerizationof olefin-based monomers using a particular transition metal compoundand co-catalyst.

The olefin-based polymer has a relatively low melting point and arelatively high crystallization temperature, compared to the previouslyknown olefin-based polymers having a molecular weight or a density at anequivalent level. Such olefin-based polymer is melted at a relativelylow melting point, and thus can be adhesive. In addition, since itscrystallization temperature is higher than the melting point, theolefin-based polymer can be more rapidly crystallized while it is cooledafter melted-processed, and can exhibit adhesive properties. As aresult, it is able to exhibit more excellent adhesive properties,processability, and processing speed than the previously knownolefin-based polymers.

Additionally, the olefin-based polymer can maintain the low density andthe relatively narrow molecular weight distribution that are suitablefor hot-melt adhesives or the like, while satisfying the above describedcharacteristics, thereby showing excellent physical properties.Therefore, the olefin-based polymer can be very desirably applied tohot-melt adhesives or the like.

The olefin-based polymer may have a weight average molecular weight (Mw)of approximately 1,000 to 80,000, preferably approximately 10,000 to50,000, and more preferably approximately 10,000 to 30,000. As theolefin-based polymer has a molecular weight in the range of such a lowlevel, it is able to show lower viscosity after melted. Consequently,the olefin-based polymer can exhibit more improved processability.

When the olefin-based polymer was prepared to have a molecular weightlower than approximately 1,000 to 30,000, the olefin-based polymer mayhave a melt index of approximately more than 500 g/10 min under a loadof approximately 2.16 kg, and a zero shear viscosity of approximately 20Pa*S or less which is measured at approximately 190° C. When theolefin-based polymer is polymerized to have a low molecular weight, itcan exhibit ultra high fluidity, satisfying the melt index and theviscosity in the above mentioned range. As the olefin-based polymerexhibits ultra high fluidity, the olefin-based polymer is able to showmore excellent processability, processing speed or the like, andtherefore can be more preferably applied to hot-melt adhesives or thelike.

As described above, the olefin-based polymer can have a relatively lowmelting point and a relatively high crystallization temperature,compared to the previously known olefin-based polymers having amolecular weight or a density at an equivalent level. More specifically,the olefin-based polymer may have a crystallization temperature Tc (°C.) of 60 to 90° C. and a melting point Tm (° C.) of 50 to 70° C., andpreferably a crystallization temperature Tc (° C.) of 60 to 80° C. and amelting point Tm (° C.) of 50 to 65° C. As the above ranges of thecrystallization temperature and the melting point are compared to thoseof the previously known olefin-based polymers at an equivalent level,the melting point is approximately 5° C. or lower and thecrystallization temperature is approximately 8° C. or higher. Inparticular, the previously known olefin-based polymers at an equivalentlevel did not satisfy the relation of Tc−Tm>0. Because of the highmelting point, the conventional olefin-based polymers were difficult toexhibit excellent adhesive properties, especially, at a low temperature.In addition, because the crystallization temperature is generally lowerthan the melting point, it is difficult to achieve high-speed processingupon melting processing, which is one of the factors that makes itdifficult to obtain excellent adhesive properties. In contrast, theolefin-based polymer of one embodiment can maintain its crystallizationtemperature and melting point in the above ranges while satisfying therelation of Tc−Tm>0, and therefore it is able to exhibit superioradhesive properties and superior processability such as high-speedprocessing due to rapid crystallization.

Meanwhile, the above mentioned olefin-based polymer may be anethylene-alpha olefin copolymer, and the alpha olefin may be one or moreselected from the group consisting of 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene,1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene. Morespecifically, the olefin-based polymer may be an ethylene-1-octenecopolymer or an ethylene-1-hexene copolymer to be more preferably usedas a hot-melt adhesive or the like.

In the ethylene-alpha olefin copolymer, the molar ratio ofethylene:alpha olefin may be 1:100 to 100:1, preferably 1:10 to 10:1,and more preferably 1:5 to 2:1. Further, the weight ratio of the alphaolefin to the total weight of the copolymer may be, for example,approximately 10 to 90% by weight, preferably approximately 20 to 80% byweight, and more preferably approximately 30 to 60% by weight. Theethylene-alpha olefin copolymer can show proper physical properties suchas relatively low density or molecular weight, as the content of thecomonomer such as alpha olefin meets the above range.

According to another embodiment of the present invention, a preparationmethod of the above mentioned olefin-based polymer is provided. Thepreparation method may include the step of polymerizing olefin-basedmonomers in the presence of a catalyst composition including atransition metal compound of the following Chemical Formula 1 and one ormore co-catalysts selected from the group consisting of the followingChemical Formulae 4 to 6:

wherein R1 and R2 are the same as or different from each other, and eachindependently hydrogen; an alkyl radical having 1 to 20 carbon atoms; analkenyl radical having 2 to 20 carbon atoms; an aryl radical having 6 to20 carbon atoms; a silyl radical; an alkylaryl radical having 7 to 20carbon atoms; an arylalkyl radical having 7 to 20 carbon atoms; or aGroup 4 metalloid radical substituted with hydrocarbyl; or R1 and R2 ortwo R2s may be connected to each other by an alkylidene radicalcontaining an alkyl radical having 1 to 20 carbon atoms or an arylradical having 6 to 20 carbon atoms so as to form a ring;

R3s are the same as or different from each other, and each independentlyhydrogen; a halogen radical; an alkyl radical having 1 to 20 carbonatoms; an alkenyl radical having 2 to 20 carbon atoms; an aryl radicalhaving 6 to 20 carbon atoms; an alkylaryl radical having 7 to 20 carbonatoms; an arylalkyl radical having 7 to 20 carbon atoms; an alkoxyradical having 1 to 20 carbon atoms; an aryloxy radical having 6 to 20carbon atoms; or amido radical; or two or more of R3s may be connectedto each other so as to form an aliphatic or aromatic ring;

CY1 is a substituted or unsubstituted aliphatic or aromatic ring, inwhich CY1 may be substituted with a halogen radical; an alkyl radicalhaving 1 to 20 carbon atoms; an alkenyl radical having 2 to 20 carbonatoms; an aryl radical having 6 to 20 carbon atoms; an alkylaryl radicalhaving 7 to 20 carbon atoms; an arylalkyl radical having 7 to 20 carbonatoms; an alkoxy radical having 1 to 20 carbon atoms; an aryloxy radicalhaving 6 to 20 carbon atoms; or an amido radical; or if a plurality ofsubstituents are present, two or more thereof may be connected to eachother so as to form an aliphatic or aromatic ring;

M is a Group 4 transition metal; and

Q1 and Q2 are the same as or different from each other, and eachindependently a halogen radical; an alkyl radical having 1 to 20 carbonatoms; an alkenyl radical having 2 to 20 carbon atoms; an aryl radicalhaving 6 to 20 carbon atoms; an alkylaryl having 7 to 20 carbon atoms;arylalkyl radical having 7 to 20 carbon atoms; an alkyl amido radicalhaving 1 to 20 carbon atoms; an aryl amido radical having 6 to 20 carbonatoms; or alkylidene radical having 1 to 20 carbon atoms,

—[Al(R8)-O]_(n)—  [Chemical Formula 4]

wherein R8s are the same as or different from each other, and eachindependently halogen; a hydrocarbon having 1 to 20 carbon atoms; or ahydrocarbon having 1 to 20 carbon atoms which is substituted withhalogen; and n is an integer of 2 or more;

D(R8)₃  [Chemical Formula 5]

wherein R8 is the same as defined in Chemical Formula 4; and D is analuminium or boron;

[L-H]⁺[ZA₄]⁻ or [L]⁺[ZA₄]⁻  [Chemical Formula 6]

wherein L is a neutral or cationic Lewis acid; H is a hydrogen atom; Zis an element of Group 13; and As are the same as or different from eachother, and each independently an aryl group having 6 to 20 carbon atoms,or an alkyl group having 1 to 20 carbon atoms, at which one or morehydrogen atoms are unsubstituted or substituted with halogen,hydrocarbon having 1 to 20 carbon atoms, alkoxy, or phenoxy.

When polymerization of olefin-based monomers (e.g., copolymerization ofethylene and alpha olefin) is performed using the transition metalcompound of Chemical Formula 1 as a catalyst and one or moreco-catalysts selected from Chemical Formulae 4 to 6, the olefin-basedpolymer satisfying the physical properties of one embodiment can beprepared. It is inferred that the co-catalyst properly activates thecatalyst of the transition metal compound so as to prevent generation ofexcessively long polymer chains, and the catalyst and the co-catalystrandomize binding of the olefin-based monomers (e.g., randomcopolymerization of ethylene and alpha olefin without formation of blockcopolymers). Consequently, the olefin-based polymer of one embodiment,which exhibits a lower melting point and a higher crystallizationtemperature, can be prepared.

On the other hand, the transition metal compound of Chemical Formula 1is more preferably a transition metal compound represented by thefollowing Chemical Formula 2 or 3, in order to control electronic andsteric environments in the vicinity of the central metal.

wherein R4s and R5s are the same as or different from each other, andeach independently hydrogen; an alkyl radical having 1 to 20 carbonatoms; an aryl radical having 6 to 20 carbon atoms; or a silyl radical;

R6s are the same as or different from each other, and each independentlyhydrogen; an alkyl radical having 1 to 20 carbon atoms; an alkenylradical having 2 to 20 carbon atoms; an aryl radical having 6 to 20carbon atoms; an alkylaryl radical having 7 to 20 carbon atoms; anarylalkyl radical having 7 to 20 carbon atoms; an alkoxy radical having1 to 20 carbon atoms; an aryloxy radical having 6 to 20 carbon atoms; oran amido radical; two or more of R6s may be connected to each other soas to form an aliphatic or aromatic ring;

Q3 and Q4 are the same as or different from each other, and eachindependently a halogen radical; an alkyl radical having 1 to 20 carbonatoms; an alkyl amido radical having 1 to 20 carbon atoms; or an arylamido radical having 6 to 20 carbon atoms;

M is a Group 4 transition metal.

In Chemical Formula 1, more preferred compounds to control theelectronic or steric environment around the central metal includetransition metal compounds of following structures:

wherein R7s are the same as or different from each other, and eachindependently selected from a hydrogen or methyl radical,

Q5 and Q6 are the same as or different from each other, and eachindependently selected from a methyl radical, a dimethylamido radical ora chloride radical.

Examples of the compound of Chemical Formula 4 used as the co-catalystinclude methylaluminoxane, ethylaluminoxane, isobutylaluminoxane,butylaluminoxane, etc. Among them, methylaluminoxane may be preferablyused.

Further, examples of the compound represented by Chemical Formula 5include trimethylaluminium, triethylaluminium, triisobutylaluminium,tripropylaluminium, tributylaluminium, dimethylchloroaluminium,triisopropylaluminium, tri-s-butylaluminium, tricyclopentylaluminium,tripentylaluminium, triisopentylaluminium, trihexylaluminium,trioctylaluminium, ethyldimethylaluminium, methyldiethylaluminium,triphenylaluminium, tri-p-tolylaluminium, dimethylaluminiummethoxide,dimethylaluminiumethoxide, trimethylboron, triethylboron,triisobutylboron, tripropylboron, tributylboron, etc. Among them,trimethylaluminium, triethylaluminium or triisobutylaluminium may bemore preferably used.

Further, examples of the compound represented by Chemical Formula 6include triethylammonium tetraphenyl boron, tributylammonium tetraphenylboron, trimethylammonium tetraphenyl boron, tripropylammoniumtetraphenyl boron, trimethylammonium tetra(p-tolyl)boron,trimethylammonium tetra(o,p-dimethylphenyl)boron, tributylammoniumtetra(p-trifluoromethylphenyl)boron, trimethylammoniumtetra(p-trifluoromethylphenyl)boron, tributylammoniumtetrapentafluorophenyl boron, N,N-diethylanilinium tetraphenyl boron,N,N-diethylanilinium tetraphenyl boron, N,N-diethylaniliniumtetrapentafluorophenyl boron, diethylammonium tetrapentafluorophenylboron, triphenylphosphonium tetraphenyl boron, trimethylphosphoniumtetraphenyl boron, octadecylmethylammoniumtetrakis(pentafluorophenyl)boron, triethylammonium tetraphenylaluminium, tributylammonium tetraphenyl aluminium, trimethylammoniumtetraphenyl aluminium, tripropylammonium tetraphenyl aluminium,trimethylammonium tetra(p-tolyl)aluminium, tripropylammoniumtetra(p-tolyl)aluminium, triethylammoniumtetra(o,p-dimethylphenyl)aluminium, tributylammoniumtetra(p-trifluoromethylphenyl)aluminium, trimethylammoniumtetra(p-trifluoromethylphenyl)aluminium, tributylammoniumtetrapentafluorophenyl aluminium, N,N-diethylanilinium tetraphenylaluminium, N,N-diethylanilinium tetrapentafluorophenyl aluminium,diethylammonium tetrapentatetraphenyl aluminium, triphenylphosphoniumtetraphenyl aluminium, trimethylphosphonium tetraphenyl aluminium,tripropylammonium tetra(p-tolyl)boron, triethylammoniumtetra(o,p-dimethylphenyl)boron, tributylammoniumtetra(p-trifluoromethylphenyl)boron, N,N-diethylanilinium tetraphenylboron, triphenylcarbonium tetra(p-trifluoromethylphenyl)boron,triphenylcarbonium tetrapentafluorophenyl boron, etc.

In the preparation method of another embodiment, the catalystcomposition including the above mentioned transition metal compound ofChemical Formula 1 and one or more co-catalysts of Chemical Formulae 4to 6 is used, and such catalyst composition can be obtained by simplymixing and contacting the transition metal compound with one or moreco-catalysts. However, the catalyst composition may include the compoundof Chemical Formula 4 or 5, together with the compound of ChemicalFormula 6. In this case, the transition metal compound is contacted withthe compound of Chemical Formula 4 or 5 so as to obtain a mixture, andthen the compound of Chemical Formula 6 is added to the mixture so as toobtain the catalyst composition.

In the preparation method, the transition metal compound and theco-catalyst may be used in the molar ratio of the transition metalcompound:the co-catalyst from 1:1 to 1:10000. When the molar ratio iswithin the above range, the co-catalyst properly activates thetransition metal while minimizing the possibility of remaining theco-catalyst in the excessive amount. Accordingly, the olefin-basedpolymer satisfying the physical properties of one embodiment can be morepreferably obtained, and the economic feasibility of the process and thepurity of the polymer can be also improved.

More specifically, if the co-catalyst includes any one of ChemicalFormulae 4 to 6, the molar ratio of the transition metal compound:theco-catalyst may be 1:1 to 1:10000, preferably 1:10 to 1:10000, morepreferably 1:100 to 1:5,000, and most preferably 1:500 to 1:2000.

Further, if the co-catalyst includes any one of Chemical Formulae 4 to 6together with the compound of Chemical Formula 6, the molar ratio of thetransition metal compound of Chemical Formula 1: the compound ofChemical Formula 4 or 5 may be 1:2 to 1:5000, preferably 1:10 to 1:1000,and more preferably 1:20 to 1:500. The compound of Chemical Formula 4 or5 alkylates the transition metal compound, and the compound of ChemicalFormula 6 activates the alkylated transition metal compound. If themolar ratio is not within the above range, the alkylation does not occurproperly or a side reaction occurs between the excessive amount of thecompound of Chemical Formula 4 or 5 and the compound of Chemical Formula6, and thus proper activation of the transition metal compound does notoccur.

Further, the molar ratio of the transition metal compound of ChemicalFormula 1:the compound of Chemical Formula 6 may be 1:1 to 1:25,preferably 1:1 to 1:10, and more preferably 1:1 to 1:5. If the molarratio is not within the above range, proper activation of the transitionmetal compound may not occur so as to decrease activity of the catalystcomposition, or the excessive amount of the activating agent may reducethe economic feasibility or the purity of the polymer.

Additionally, when the molar ratio of the transition metal compound:theco-catalyst is more than 1:10, for example, 1:10 to 1:10000, that is, arelatively high amount of the co-catalyst is used, and hydrogen gas isinjected at a flow rate of for example, 3.00 L/h or more, preferably3.00 to 10.0 L/h in the polymerization step, the olefin-based polymerwith ultra-high fluidity can be prepared. The olefin-based polymer withultra-high fluidity thus prepared may have a melt index of more thanapproximately 500 g/10 min under a load of approximately 2.16 kg and azero shear viscosity of approximately 20 Pa*S or less which is measuredat approximately 190° C.

To prepare the olefin-based polymer with ultra-high fluidity, its weightaverage molecular weight should be as low as 1,000 to 30,000. When therelatively high amount of the co-catalyst is used and hydrogen gas isadded, early termination of polymer chain extension can be achieved.Consequently, the above mentioned low-molecular weight olefin-basedpolymer with ultra-high fluidity can be prepared, and this polymer isable to exhibit more improved processability and processing speed.

In order to prepare the above mentioned catalyst composition, thetransition metal compound and the co-catalyst may be dissolved in asolvent, and the solvent may be a hydrocarbon solvent such as pentane,hexane and heptane, or an aromatic solvent such as benzene and toluene.In addition, the transition metal compound and the co-catalyst may beused as supported on a support such as silica, alumina or the like.

As described above, the olefin-based polymer may be an ethylene-alphaolefin copolymer. In order to prepare this copolymer, polymerization maybe performed using alpha olefin selected from the group consisting of1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene,1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and1-eicosene, together with ethylene, as the olefin-based monomers.

In the preparation method of the polymer, a scavenger is further usedtogether with the above mentioned catalyst composition so as to performthe polymerization step. The scavenger may be exemplified by a compoundrepresented by the following Chemical Formula 7, and other variousscavengers may be also used:

D(R)₃  [Chemical Formula 7]

wherein Rs are each independently halogen; hydrocarbon having 1 to 20carbon atoms; or hydrocarbon having 1 to 20 carbon atoms which issubstituted with halogen; and D is aluminium or boron.

Specific examples of the scavenger include trimethylaluminium,triethylaluminium, triisobutylaluminium, tripropylaluminium,tributylaluminium, dimethylchloroaluminium, triisopropylaluminium,tri-s-butylaluminium, tricyclopentylaluminium, tripentylaluminium,triisopentylaluminium, trihexylaluminium, trioctylaluminium,ethyldimethylaluminium, methyldiethylaluminium, triphenylaluminium,tri-p-tolylaluminium, dimethylaluminiummethoxide,dimethylaluminiumethoxide, trimethylboron, triethylboron,triisobutylboron, tripropylboron, tributylboron, etc. Among them,trimethylaluminium, triethylaluminium, or triisobutylaluminium may bemore preferably used.

The scavenger may be injected to a reactor separately with the abovementioned catalyst composition, and it may be used in a typical amountpreviously known so as to improve yield of the polymer.

In the preparation method of the olefin-based polymer, thepolymerization step may be carried out under the typical reactionconditions for olefin-based polymers. First, the polymerization step maybe carried out by a continuous solution polymerization process.

In such polymerization process, the above mentioned catalyst compositionand olefin-based monomers, and optionally the scavenger are firstintroduced to the reactor. The solvent for polymerization reaction isinjected to the reactor. Thus, a mixture of the solvent, the catalystcomposition, the olefin-based monomers, and optionally the scavenger ispresent in the reactor.

The solvent for polymerization reaction may include an aliphatichydrocarbon solvent having 5 to 12 carbon atoms such as pentane, hexane,heptane, nonane, decane, and isomers thereof; an aromatic hydrocarbonsolvent such as toluene and benzene; a hydrocarbon solvent substitutedwith chlorine such as dichloromethane and chlorobenzene; and mixturesthereof, but is not limited thereto. However, the preferred solvent isn-hexane, considering polymerization reactivity.

When ethylene and alpha olefin are used as the olefin-based monomers,the molar ratio of ethylene:alpha olefin may be 1:100 to 100:1, asdescribed above. If the molar ratio is not within the above range, it isdifficult to achieve the physical properties of one embodiment such asthe low density, as described above. Also, since the residual amount ofthe unreacted alpha olefin is too large, the conversion rate isdecreased, and consequently the process recycling may be increased.

The solvent for polymerization reaction may be used in the molar ratioof ethylene:solvent from 1:10000 to 10:1, and preferably from 1:100 to5:1, which is a ratio suitable for dissolving the olefin-based monomers,smooth transportation of the produced copolymer, and improvement ofeconomic feasibility of the equipment and the process.

The solvent is injected at −40 to 150° C. using a heater or freezer, andthus polymerization reaction is initiated with the mixture of themonomers and the catalyst composition. If the solvent temperature islower than −40° C., the solvent temperature is too low, and the reactiontemperature is also decreased, and thus it is difficult to control thetemperature, even though there is some difference depending on thereaction amount. If the solvent temperature is higher than 150° C., thesolvent temperature is too high, and thus it is difficult to control theheat of reaction.

Further, the pressure is increased to 50 bar or higher using ahigh-capacity pump installed in the reactor, and then the materials(solvent, monomer, catalyst composition, etc.) are supplied, therebypassing the mixed material through the reactor without arrangement ofreactor, and additional pumping between a pressure drop device and aseparator.

The internal pressure of the reactor is 1 to 300 bar, preferably 30 to200 bar, and most preferably 50 to 100 bar. If the internal pressure isless than 1 bar, the reaction rate is lowered to reduce the productivityand vaporization of the solvent is caused. If the internal pressure ismore than 300 bar, the equipment cost is increased due to high pressure.

The olefin-based polymer prepared by the above mentioned method exhibitsexcellent adhesive properties and processability, thereby being verypreferably used in hot-melt adhesives or the like, and in particular, itcan be used in various applications such as packaging for vehicles,electric wires, toys, fibers, and medical materials, constructionmaterials, and housewares.

Hereinafter, the present invention will be described in more detail withreference to the following Examples. However, these Examples are forillustrative purposes only, and the scope of the present invention isnot intended to be limited by these Examples.

EXAMPLE Examples 1 to 5 Preparation of Ethylene-Alpha Olefin Copolymer

A hexane solvent, ethylene, and 1-octene monomers were supplied into a1.5 L continuous stirred reactor which was preheated to 100 to 150° C.at a pressure of 89 bars. A[(7-Methyl-1,2,3,4-tetrahydroquinolin-8-yl)trimethylcyclopentadienyl-eta5,kappa-N]titanium dimethyl compound belonging to the category of Chemical Formula1 (LGC001, LG Chem), an octadecylmethylammoniumtetrakis(pentafluorophenyl)boron co-catalyst, and a trimethylaluminiumscavenger were supplied from a catalyst storage tank to the reactor toperform copolymerization reaction. The polymerization was performed atthe temperature of the following Table 1. The pressure of polymersolution produced by the copolymerization reaction was reduced to 7 barat the end of the reactor, and then supplied into a solvent separatorwhich was preheated to 230° C. to remove almost of the solvent by asolvent separation process. The residual solvent was completely removedfrom the copolymers, which were supplied into a second separator by apump, using a vacuum pump, and then the copolymer was passed throughcooling water and a cutter to give particulate polymers. Thepolymerization conditions of Examples 1 to 5 are summarized in thefollowing Table 1.

TABLE 1 Exam- Exam- Exam- ple 1 Example 2 ple 3 Example 4 ple 5 Hx(kg/h) 3.36 3.36 3.36 3.36 3.36 Ethylene (kg/h) 0.63 0.63 0.63 0.63 0.631-Octene (kg/h) 0.55 0.55 0.55 0.55 0.55 Catalyst (μmol/min) 0.50 0.500.50 0.50 0.50 Co-catalyst 3.00 3.00 3.00 3.00 6.00 (μmol/min) Scavenger20 20 20 20 20 (μmol/min) H₂ (L/h) 0.80 1.00 2.00 3.00 3.00 Temperature(° C.) 155 155 153 152 153 Pressure (bar) 89 89 89 89 89

Comparative Examples 1 to 3 Commercialized Ethylene-Alpha OlefinCopolymer

An ethylene-alpha olefin copolymer, EG8200 commercialized by Dowchemical was used as Comparative Example 1, GA1950 was used asComparative Example 2, and GA 1900 was used as Comparative Example 3.

Experimental Example 1 Measurement of Physical Properties ofEthylene-Alpha Olefin Copolymer

Density, melt index (MI_(2.16)), molecular weight, molecular weightdistribution (PDI), crystallization temperature, melting point,comonomer (alpha olefin) content, and shear rate viscosity of theethylene-alpha olefin copolymers of Examples 1 to 5 and ComparativeExamples 1 to 3 were measured as follows:

(1) Density: measured in accordance with ASTM D792

(2) Melt index (MI₂₁₆): measured in accordance with ASTM D1238

(3) Molecular weight and molecular weight distribution (PDI): measuredby high-temperature GPC (PL-GPC220)

(4) Comonomer content: measured by ¹³C-NMR

(5) Melting point (Tm): the temperature was increased to 200° C.,maintained at that temperature for 5 minutes, and decreased to 30° C.Then, the temperature was increased again and the summit of the DSC(Differential Scanning calorimeter, manufactured by TA) curve wasdetermined as the melting point. The temperature was increased anddecreased at a rate of 10° C./min, and the melting point was obtained ina second temperature increase period.

(6) Crystallization temperature (Tc): the temperature was decreasedunder the same conditions as in the melting point and the summit of theDSC (Differential Scanning calorimeter, manufactured by TA) curve wasdetermined as the crystallization point.

(7) Shear rate viscosity: viscosity changes of the melted copolymerswere measured at 190° C. with increasing shear rate using a capillaryrheometer.

The results of measuring density, melt index (MI_(2.16)), molecularweight, molecular weight distribution (PDI), crystallizationtemperature, melting point, and comonomer content of the ethylene-alphaolefin copolymers of Examples 1 to 5 and Comparative Examples 1 to 3 aresummarized in the following Table 2, and the results of measuring shearrate viscosity of Examples 1, 4 and 5 are depicted in FIG. 1.

TABLE 2 Comonomer Density MI_(2.16) Tm Tc Tc- content (g/cm³⁾ (g/10 min)Mw PDI (° C.) (° C.) Tm (wt %) Comparative 0.870 5.0 77067 2.03 62.345.1 −17.2 Example 1 Comparative 0.874 500 23692 2.00 73.7 56.5 −17.2Example 2 Comparative 0.870 1000 20404 2.00 69.5 53.1 −16.4 Example 3Example 1 0.870 5.0 76220 2.15 54.9 62.7 7.8 36.35 Example 2 0.870 1155977 2.18 53.7 67.3 13.6 36.14 Example 3 0.870 18 48458 2.20 57.6 72.014.4 35.28 Example 4 0.870 48 37277 2.25 58.1 78.1 20 35.28 Example 50.870 More than 21872 2.23 62.4 77.9 15.5 35.06 500

Referring to Table 2, it was found that the copolymers of Examples 1 to5 exhibited a relatively narrow PDI, a relatively high crystallizationtemperature, and a relatively low melting point, while showing thedensity and molecular weight at an equivalent level to those ofComparative Examples 1 to 3.

Accordingly, it is expected that the copolymers of Examples 1 to 5 aremelted at a relatively low melting point or higher so as to showadhesive properties, and its rapid crystallization occurs at atemperature higher than the melting point, thereby showing excellentadhesive properties and processing speed. In contrast, since thecopolymers of Comparative Examples 1 to 3 have a relatively high meltingpoint and a relatively low crystallization temperature, it is difficultto show adhesive properties equivalent to those of Examples. Also, therapid crystallization does not occur in the melt state andprocessability is poor.

Referring to FIG. 1 and Table 2, the polymer of Example 5, which wasprepared by increasing the hydrogen injection amount and the ratio ofthe co-catalyst, had a melt index of more than 500 g/10 min under a loadof 2.16 kg and a zero shear viscosity of approximately 10 Pa*S which wasderived from FIG. 1, indicating ultra-high fluidity. Thus, it was foundthat the polymer is able to show superior processability and processingspeed.

Experimental Example 2 Test on Adhesive Properties of Ethylene-AlphaOlefin Copolymer

The adhesive properties of the ethylene-alpha olefin copolymers ofComparative Examples 2 and 3 and Example 5 were compared by a peel testmethod. A sample solution prepared by swelling the copolymer in a hexanesolvent was coated on a PET resin film with an area of 1 inch, and thenthe hexane solvent was volatilized and removed in a 100° C. oven for 2minutes. The thickness of the applied sample, from which the hexanesolvent was removed, was approximately 30 μm. The sample-coated PETresin film thus prepared was attached on a stainless steel with an areaof 1 inch by applying a pressure at 100° C. for 20 minutes, and slowlycooled to room temperature. Adhesive strength was measured by a peeltest using a texture analyzer (manufactured by TA, TA-XT plus). The testwas repeated 4 times for each sample, and the mean value was determinedfor the measurement result. The results of the adhesive strength testare shown in the following Table 3.

TABLE 3 Adhesive strength (g/inch) Comparative Example 2 9 ComparativeExample 3 17 Example 5 1614

Referring to Table 3, the copolymer of Example 5 satisfying thepredetermined molecular weight distribution and density and the relationof Tc−Tm>0 was found to show very excellent adhesive strength. Incontrast, the copolymers of Comparative Examples 2 and 3 were found toshow poor adhesive strength.

What is claimed is:
 1. An olefin-based polymer having a melt index undera load of 2.16 kg of more than 500 g/10 min and a zero shear viscosityof 20 Pa*S or less, and satisfying the relation of Tc−Tm>0, wherein Tc(° C.) is a crystallization temperature and Tm (° C.) is a meltingpoint.
 2. The olefin-based polymer according to claim 1, wherein itsweight average molecular weight (Mw) is 1,000 to 80,000.
 3. Theolefin-based polymer according to claim 1, having a molecular weightdistribution (Mw/Mn, PDI) of 2˜3 and a density of 0.85 to 0.88 g/cm³. 4.The olefin-based polymer according to claim 1, wherein itscrystallization temperature Tc (° C.) is 60 to 90° C., and its meltingpoint Tm (° C.) is 50 to 70° C.
 5. The olefin-based polymer according toclaim 1, wherein it is an ethylene-alpha olefin copolymer.
 6. Theolefin-based polymer according to claim 5, wherein the alpha olefinincludes one or more selected from the group consisting of 1-butene,1-pentene, methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene,1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-itocene. 7.The olefin-based polymer according to claim 5, wherein the molar ratioof ethylene:alpha olefin is 1:100 to 100:1.